Filter Press Operation

Filtration Process

• The filtration process involves introducing compressed air to inflate the membrane, speeding up the filtration process once the filtrate discharge is reduced.
• The compressed air is released, and the hydraulic pump is opened, shifting the filter plates and discharging the cake.
• The filter press should be installed in a shaded area to prevent direct sunlight, as the filter plates and cloths are made of polypropylene material sensitive to UV light.

Pressure Drop of Fluid Through Filter Cake

• The flow of filtrate through the packed bed of cake can be described by an equation similar to Poiseuille's law, assuming laminar flow: ∆P = 2aµ / (LD)
• Where a is a constant, ∆P is the pressure drop, L is the thickness of the cake, D is the filter cross-sectional area, and µ is the linear velocity.

Filtration Equation for Constant-Pressure Filtration

• The basic equation for filtration rate in a batch process is:
  • dv/dt = 2 KP / A (-∆P) V + B
• Where KP is a constant, A is the filter cross-sectional area, ∆P is the pressure drop, V is the total filtration volume, and B is a constant.

Theory of Filtration

• The filtration equation can be integrated to obtain the filtration time: t = (KP / 2) V^2 + BV
• A plot of t/V vs V will be linear, with a slope equal to KP/2 and an intercept of B.

Washing of Filter Cakes and Total Cycle Time

• The washing of a cake after the filtration cycle takes place by displacement of the filtrate and by diffusion.
• The washing rate can be calculated using the equation: (dv/dt)f = 1 / (KF Vf + B)
• Where (dv/dt)f is the rate of washing, KF is a constant, Vf is the final filtration volume, and B is a constant.

Experimental Equipment

• The Amston filter press is designed to be simple and easy to operate, with a construction that allows for easy maintenance without disturbing the feed and filtrate piping.
• The stationary and moving platen are manufactured from thick mild steel plates to provide a rigid and accurate closing of the filter press with minimal leakage.

Start-Up and Operating Procedures

• The start-up procedures include checking the filter plate sequence, filter cloth arrangement, and filtrate outlet valves.
• The operating procedures include closing the filter press, operating the hydraulic hand pump, and tightening the locking wheel to secure the hydraulic ram in position.

Results and Report

• The experiment results include calculating the volume of cake collected, the weight of the wet cake, the percentage of water remaining in the wet cake, and the percentage of calcium carbonate recovery.
• The experiment data is used to determine the parameters KP, B, a, and Rm, and to discuss the results.
• The unit of filter-medium resistance is not specified.
• The septum in any filter must meet specific requirements, including being able to withstand the operating pressure and having a smooth surface to prevent cake from building up.
• The principles of cake filtration include the use of pressure difference to force the liquid through the filter cloth and cake, and the use of a filter medium to separate the solid and liquid phases.